Influence of cromolyn sodium on airway temperature in normal subjects

It is well established that cromolyn sodium attenuates the bronchoconstriction induced by airway cooling in both normal and asthmatic subjects. To determine whether this protection derives from a modification of the thermal events that transpire during the conditioning of inspired air, we first recorded the effect of cromolyn on the bronchoconstrictor response to hyperventilation with frigid air in 7 normal subjects. On a separate occasion, we imposed the same thermal burden and measured the temperature at multiple sites within the airways before and after pretreatment with cromolyn. The first cold air challenge produced a significant decrease in forced expiratory volume in one second (FEV1) of 5.5 +/- 0.9% (SEM) and these changes were significantly reduced by cromolyn (FEV1 = 2.8 +/- 0.9%; p less than 0.05). In concert with the improvement in mechanics, the temperatures (T) within the trachea (tr) and the anterior segment of the right lower lobe (AS-RLL) were significantly higher after cromolyn (Ttr = 1.3 +/- 0.2 degrees C; p less than 0.01; TAS-RLL = 1.0 +/- 0.4 degrees C; p = 0.05), and there was a direct positive relationship between the mechanical protection offered by the drug and the increase in airway temperature (Spearman's rank correlation coefficient = 0.83; p = 0.05). These data suggest that cromolyn modifies respiratory heat exchange in such a fashion as to limit airway cooling. The mechanism of this action is not presently known but may reflect a direct or indirect influence on the bronchial vasculature.